1. Technical Field
The present disclosure relates to a power supply system or battery system, which can be used in a hybrid electric vehicle.
2. Background Art
A battery for a hybrid electric vehicle may include many cells electrically connected. To attain a battery of a sufficiently high voltage, cells are electrically connected serially. Groups of several cells can be coupled longitudinally and then placed in a housing with groups arranged in parallel compartments. And, although cell groups are physically arranged in a parallel fashion, they may be electrically coupled either in series or in parallel. Groups of individual cells within a housing can be called a brick. A plurality of bricks are arranged in an array and electrically connected via bus bars to provide the desired voltage and current characteristics for the particular application. Such connected plurality of bricks forms a battery.
To avoid shorts among cells within a group due to longitudinal bending within a cell group, it is known to place insulating sleeves over the connection points. Such sleeves increase the diameter of the battery group and thus the compartments within the housing. As the battery includes many cells arranged in an array, any increase in diameter is multiplied and causes the housing to be larger than it might otherwise be.
To ensure a robust connection, the longitudinally-arranged cell groups may be welded together. When cells are combined longitudinally to form a group, any manufacturing variation in length of the cells and any variation in the length of the cell group in forming the joint between cells will result in an overall increase in cell group stackup variation. Bus bars, which are used to electrically connect cell groups, may be forced to bend to accommodate differences in length between connecting cells groups. By forcing the bus bar to bend, the connection may be compromised and harm the integrity of the battery. It is desirable to minimize the amount of stackup tolerance that the bus bar bending accommodates.
During charging and discharging of the battery, energy is generated within the cells. The battery is cooled to maintain the temperature within individual cells below a temperature at which cells are damaged. Typically, temperature sensors are provided at various locations within the battery from which temperature within the cells is estimated. It is important to locate the temperature sensors at locations that provide a good indication of the maximum temperatures experienced within battery cells. Also, it is desirable for the temperature sensors to be located in a position that is readily accessible after much of the assembly of the battery is completed because wires from the temperature sensor may be damaged during assembly.